Zinc is essential for growth and reproduction of animals and i t has been suggested that the most critical requirement for Zn is for alteration in the genetic expression of cells (Chesters, 1978). However, in EDTA-treated lymphocyte cultures, lack of Zn delayed maturation of 32s ribosomal RNA precursor to 28s ribosomal RNA and reduced survival of the 28s RNA (Chesters, 1975). This alteration in...

Previously, we found that gene expressions for ribosomal RNA differ in tumorous and normal cells, so we compared the distributions of ribosomal cistrons in subfractions of nuclei from Ehrlich ascites tumor and mouse liver cells. The mean number of nucleoli per nucleus is mouse liver (diploid cells) is 3.7 while, in hyperdiploid and hypotetraploid strains of Ehrlich ascites tumors, the means are...

In Saccharomyces cerevisiae, 59 of the 78 ribosomal proteins are encoded by duplicated genes that, in most cases, encode identical or very similar protein products. However, different sets of ribosomal protein genes have been identified in screens for various phenotypes, including life span, budding pattern, and drug sensitivities. Due to potential suppressors of growth rate defects among this ...

Protein biosynthesis is one of the key elements of gene expression in living cells. All proteins are synthesized on ribonucleoprotein complexes, the ribosomes. In bacteria and their derivatives— eukaryotic mitochondria and plastids— ribosomes consist of a small and a large subunit which together comprise more than 50 ribosomal proteins and usually two to four ribosomal RNAs (rRNAs). Synthesis o...

We identified 34 new ribosomal protein genes in the Schizosaccharomyces pombe database at the Sanger Centre coding for 30 different ribosomal proteins. All contain the Homol D-box in their promoter. We have shown that Homol D is, in this promoter type, the TATA-analogue. Many promoters contain the Homol E-box, which serves as a proximal activation sequence. Furthermore, comparative sequence ana...

Despite the emergence of a large number of X-ray crystallographic models of the bacterial 70S ribosome over the past decade, an accurate atomic model of the eukaryotic 80S ribosome is still not available. Eukaryotic ribosomes possess more ribosomal proteins and ribosomal RNA than do bacterial ribosomes, which are implicated in extraribosomal functions in the eukaryotic cells. By combining cryo-...

1. Ribonuclease II of Escherichia coli degrades pulse-labelled RNA associated with ribosomes and polyuridylic acid on ribosomes and in solution to mononucleotides. 2. Ribosomal and pulse-labelled RNA in solution and ribosomal RNA in chloramphenicol particles (protein-deficient ribosomes) are degraded to oligonucleotides. 3. Ribosomal RNA in mature ribosomes is not attacked by the enzyme. 4. Fro...

Cordycepin is an analogue of adenosine lacking the 3'-OH. When incorporated into a growing RNA molecule, cordycepin prevents further elongation, thus producing a prematurely terminated RNA molecule. When HeLa cells are exposed to low concentrations of cordycepin, DNA and protein synthesis are unaffected during short exposure periods. The synthesis of completed ribosomal and ribosomal-precursor ...

Nuclear import usually relies on the presence of nuclear localization sequences (NLSs). NLSs are recognized by NLS receptors (importins), which target their substrates to the nuclear pore. We identified the NLSs of the yeast ribosomal proteins S22 and S25 and studied the former by mutational analysis. Furthermore, in S25 the nucleolar targeting information was found to overlap with its NLS. Com...

Ribosomal stress such as disruption of rRNA biogenesis activates p53 by release of ribosomal proteins from the nucleoli, which bind to MDM2 and inhibit p53 degradation. We found that p53 activation by ribosomal stress requires degradation of MDMX in an MDM2-dependent fashion. Tumor cells overexpressing MDMX are less sensitive to actinomycin D-induced growth arrest due to formation of inactive p...